Imagine if scientists discovered a toxic substance that increased the risks of cancer, diabetes and heart, lung and liver disease for millions of people. Something that also increased one’s risks for smoking, drug abuse, suicide, teen pregnancy, sexually transmitted disease, domestic violence and depression — and simultaneously reduced the chances of succeeding in school, performing well on a job and maintaining stable relationships? It would be comparable to hazards like lead paint, tobacco smoke and mercury. We would do everything in our power to contain it and keep it far away from children. Right?

Well, there is such a thing, but it’s not a substance. It’s been called “toxic stress.” For more than a decade, researchers have understood that frequent or continual stress on young children who lack adequate protection and support from adults, is strongly associated with increases in the risks of lifelong health and social problems, including all those listed above.In the late 1990s, Vincent Felitti and Robert Anda conducted a landmark study that examined the effects of adverse childhood experiences (ACEs) — including abuse, neglect, domestic violence and family dysfunction — on 17,000 mainly white, predominately well-educated, middle class people in San Diego. They found a powerful connection between the level of adversity faced and the incidence of many health and social problems. They also discovered that ACEs were more common than they had expected. (About 40 percent of respondents reported two or more ACEs, and 25 percent reported three or more.) Since then, similar surveys have been conducted in several states, with consistent findings.

In the years since, advances in biology, neuroscience, epigenetics and other fields have shed light on the mechanisms behind this phenomenon. “What the science is telling us now is how experiencegets into the brain as it’s developing its basic architecture and how it gets into the cardiovascular system and the immune system,” explains Jack P. Shonkoff, director of the Center on the Developing Child at Harvard University, where the term toxic stress was coined. “These insights provide an opportunity to think about new ways we might try to reduce the academic achievement gap and health disparities — and not just do the same old things.”

First, it’s important to note that toxic stress is not a determinant, but a risk factor. And while prevention is best, it’s never too late to mitigate its effects. It’s also critical to distinguish between “toxic stress” and normal stress. In the context of a reasonably safe environment where children have protective relationships with adults, Shonkoff explains, childhood stress is not a problem. In fact, it promotes healthy growth, coping skills and resilience. It becomes harmful when it is prolonged and when adults do not interact in ways that make children feel safe and emotionally connected.This distinction is critical, because it opens the way to new opportunities to prevent a cascade of health problems. It is exceedingly difficult to alter the environments that produce major stress for families, particularly poverty. However, children can be shielded from the most damaging effects of stress if their parents are taught how to respond appropriately. “One thing that is highly protective is the quality of the relationship between the parent and the child,” explains Darcy Lowell, an associate clinical professor at Yale University School of Medicine and the founder of Child First, a program based in Shelton, Conn., that has marshaled strong evidence demonstrating the ability to intervene early, at relatively low cost, to reduce the harm caused by childhood stress in extremely high-need families. “Early relationships, where adults are responsive and attentive, are able to buffer the damaging effects on the brain and body,” she says.Child First, initially developed at Bridgeport Hospital in Connecticut, now works in partnership with community-based agencies in 15 locations across the state, where staff members deliver its program of home-based parent guidance and child-parent psychotherapy. In awell-controlled study, children served by Child First were compared with those receiving usual social services and were found to be significantly less likely to have language problems and aggressive and defiant behaviors. Their mothers had markedly less depression and mental health problems, and the families were less likely to be involved with child protective services even three years later.